Paintable adhesion promoter system for polyvinyl chloride plastisols

ABSTRACT

Disclosed is an improved plastisol composition comprising a finely-divided vinyl chloride polymer, filler, a primary plasticizer, and a polyaminoamide-polyimidazoline adhesion promoter. The improvement for overcoating said plastisol with an acid catalyzed topcoat comprises a plasticizer/promoter phase which comprises said primary plasticizer, said adhesion promoter, and an effective amount of a secondary plasticizer non-ionic solvent effective in solvating the adhesion promoter in the plasticizer/promoter phase. The plasticizer/promoter phase is pre-formed for addition with the remaining ingredient for the plastisol composition.

This application is a division of application Ser. No. 06/092,936 filed Sept. 2, 1986.

BACKGROUND OF THE INVENTION

The present invention relates to plastisols in general and in particular to improved adhesion promoter systems for polyvinyl chloride (PVC) plastisols.

Vinyl chloride homopolymers (PVC) and copolymers are widely used for the protection of metallic surfaces against corrosion, for adhering thin sheet metal constructions, and for sealing welded seams, particularly in the automotive industry. Such coatings principally are applied in the form of plasticized vinyl chloride polymers (plastisols) by a variety of techniques. Depending upon the viscosity of the PVC plastisol, its utilization can be characterized as a sealant, caulk, coating, adhesive, or other function.

Since resistance to corrosion is a prime prerequisite in dealing with metal parts, the PVC plastisol should adhere to the metal part with a fair degree of tenacity; otherwise, oxidation undercutting would result. Despite the ability to control the texture of the plastisol by suitable fillers and the color by the addition of suitable tinctorial pigments, of the PVC plastisol must be overcoated with a high performance, e.g. acrylic, topcoat, especially in automotive uses of the PVC plastisol. Uniformity in visual appearance dictates such overcoating requirement typically.

Another requirement of the PVC plastisol is that it be curable at short, low bake cycles. In fact, successful plastisols and organisols in the automotive industry are being called on today to be curable, dry to the touch, at baking temperatures of less than 300°, e.g. about 275° F., with oven residence times of about 20-30 minutes. Energy costs dictate such low temperature, short baking cycles. Further, successful plastisol and organisol formulations must be economic and expel a minimum of atmospheric pollutants.

While a variety of adhesion promoters have been proposed for PVC plastisols and organisols, most have suffered from a variety of drawbacks including cost, insufficient film flexibility, or the like. One class of adhesion promoters which appears to exhibit a good balance between cost, flexibility, and low temperature bake characteristics are polyaminoamide-polyimidazoline adhesion promoters, such as set forth in U.S. Pat. No. 4,146,520. Such adhesion promoters have enabled the formulation of advantageous PVC plastisols and organisols which can be baked at temperatures as low as about 250° F. Unfortunately, the plastisols and organisols containing such polyaminoamide-polyimidazole adhesion promoters are not readily overcoated with acid-catalyzed topcoats, especially high performance acid catalyzed acrylic automobile finishes. It is theorized that the amine value of the adhesion promoters interacts and renders ineffectual the acid catalyst in the topcoat, thus resulting in tacky films. While reduction of the level of the adhesion promoter can overcome such topcoat tackiness, loss of adhesion also can occur at such low adhesion promoter levels. Thus, there is a need in the art to enable the utilization of polyaminoamide-polyimidazoline adhesion promoters in low bake PVC plastisol and organisol compositions, yet provide the ability to overcoat such plastisols with acid catalyzed topcoats.

BROAD STATEMENT OF THE INVENTION

The present invention is addressed to the need in the art to retain advantageous low bake properties of PVC plastisols and their requisite good adhesion to metal, yet still be able to be coated wet-on-dry or wet-on-wet by acid catalyzed topcoats. Accordingly, the present invention is directed to plastisol compositions comprising finely-divided vinyl chloride polymer, filler, a primary plasticizer, a polyaminoamide-polyimidazoline adhesion promoter. The improvement of the present invention comprises a plasticizer/promoter phase comprising said primary plasticizer, said adhesion promoter, and an effective amount of a secondary plasticizer nonionic solvent effective in solvating said adhesion promoter in said plasticizer/promoter phase wherein the plasticizer/promoter phase is preformed for addition with the remaining ingredients of the plastisol composition. Suitable nonionic secondary plasticizer solvents include aromatic solvents and polyalkylene glycol ether solvents which are effective in solvating the polyaminoamide-polyimidazoline adhesion promoters.

Another aspect of the present invention involves the method for formulating the improved plastisol compositions wherein the plasticizer/promoter phase comprising the primary plasticizer, the adhesion promoter, and the secondary plasticizer nonionic solvent is pre-formed and then such phase added to the remaining ingredients of the plastisol composition.

Advantages of the present invention include the retention of low bake characteristics of the plastisol and the excellent adhesion characteristics of the plastisol. A further advantage is the ability to overcoat the plastisol wet-on-dry or wet-on-wet with an acid catalyzed topcoat (i.e. "paintability", for present purposes) which is dry to the touch at lower bake temperatures of about 250°-360° F., for example. A further advantage is the ability to exhibit the foregoing advantageous characteristics while retaining the flexibility of controlling the rheological characteristics of the plastisol. A further advantage is an improved plastisol composition which exhibits excellent controlled age characteristics. These and other advantages will be readily apparent to those skilled in the art based upon the disclosure contained herein.

DETAILED DESCRIPTION OF THE INVENTION

The polyaminoamide-polyimidazoline adhesion promoters are set forth in U.S. Pat. No. 4,146,520. Such adhesion promoters include condensation products formed between a polymerized fatty acid mixture and an excess of polyalkylene polyamine. Such adhesion promoters additionally include the foregoing condensation product further reacted with an aldehyde, a ketone, or an epoxy compound.

While not intending to be bound by theory, it appears that a significant quantity of the adhesion promoter migrates to the surface of the cured plastisol. While such migration does not adversely impact the performance of the plastisol, it does adversely affect the curability of acid catalyzed topcoats which then are applied to the wet (wet-on-dry) or dry (i.e. wet-on-dry) plastisol. It is believed that the amine value of the adhesion promoter reacts with the acid catalyst in the topcoat which means that the topcoat will not be fully cured at the recommended bake temperatures of about 300° F. or thereabouts. As noted above, such undesirable interaction can be mostly obviated by a reduction of the amount of adhesion promoter in the plastisol, though such reduction compromises the degree of adhesion achievable, so that this alternative is not commercially viable. The same holds true for increasing the amount of acid catalyst in the acid catalyzed topcoat.

One way of viewing the result of the invention is that the adhesion promoter is rendered more compatible or homogeneous in the plastisol so that it does not overconcentrate at the film surface. Accordingly, appropriate secondary plasticizer solvents or diluents should be effective in solvating the polyaminoamide-polyimidazoline adhesion promoters. Next, such secondary plasticizer solvents should be non-ionic. Solvents rich in amine value, for example, should be avoided even though they may effectively solvate the adhesion promoters as such solvents only contribute to the problem being solved. Accordingly, nonionic solvents are recommended.

Suitable nonionic solvents which solvate the adhesion promoter include aromatic solvents and polyalkylene glycol ether solvents. By "solvate", we mean that a clear, stable solution results upon the mixing of the nonionic solvent and the adhesion promoter, typically at room temperature though modeate heating may be employed. Suitable such nonionic solvents include, for example, monoisopropyl biphenyl, diethylene glycol monoethyl ether, diisopropyl biphenyl, phenylxyleyl ethane, butylated biphenyl, and the like and mixtures thereof. The proportion of the secondary plasticizer solvent is adjusted to accomplish its function in the formulation. Often, this means between about 10 and 70 phr nonionic solvent is used.

The remaining ingredients in the plastisol are conventional and include finely-divided polyvinyl chloride homopolymers or vinyl chloride copolymers, and often blends thereof. The primary plasticizer most often will be an alkyl phthlate such as dihexyl phthlate, diisodecyl phthlate, and the like. Alternatively, the primary plasticizer may be an alkyl adipate (e.g. di(2-ethyl hexyl) adipate) or the like. The plasticizer typically will range from about 20 to 200 phr (weight parts per 100 weight parts of PVC resin).

Additionally the plastisol will contain a filler for control of rheology, control of cost, and the like. Suitably fillers include, for example, calcium carbonate, glass (including hollow glass spheres), talc, chalk, barium sulfate, and the like. The fillers certainly affect paintability of the plastisol, though with the invention more flexibility in filler utilization is gained. The proportion of filler can range up to about 300 phr and the optimum will vary depending upon the type of PVC and plasticizer, and the rheology desired. Finally, thixotropic agents can be added to achieve certain plastisol rheologies and such agents include, for example, fumed silica, bentonite, metallic fatty acid soaps, and the like. Thixotropic agents typically are added in the range of about 1-5 phr.

In order to maximize the paintability of the plastisol (i.e. ability to coat the plastisol with an acid catalyzed topcoat), it has been determined that a pre-blend of adhesion promoter, primary plasticizer, and nonionic secondary plasticizer solvent should be made. Such plasticizer/promoter blend then is added to the remaining ingredients for forming the plastisol. Apparently, the formation of the plasticizer/plastisol blend is more effective in compatibilizing the adhesion promoter in the plastisol is "pushing" the plasticizer into the PVC particles. Regardless of the mechanism involved, it has been determined that paintability of plastisol becomes a routine achievement when the plasticizer/promoter blend is initially formed in making the plastisol composition.

The plastisol is dryable or curable at very low bake temperatures ranging on down to about 250°-275° F. The plastisol either can be baked and then topcoated (wet-on-dry) or the plastisol can be applied followed by the topcoat wherein both coatings then are cured in a single bake (wet-on-wet). In automotive applications, the plastisol typically is drawn down or applied onto a metal subsrate which has been primed with a corrosion-inhibiting coating. Typical topcoats include high performance acrylic topcoats which are cured by conventional acid catalysts.

The following examples show how the present invention has been practiced but should not be construed as limiting. All percentages and proportions are by weight unless expressly indicated. Also, all citations disclosed herein are incorporated expressly herein by reference.

EXAMPLES EXAMPLE 1

The efficacy of polyaminoamide-polyimidazoline adhesion promoters in PVC plastisol formulations was demonstrated on the following general formulation.

                  TABLE 1                                                          ______________________________________                                         Ingredient*       Amount (wt.-parts)                                           ______________________________________                                         Occidental 6482   60                                                           Borden VC265      40                                                           Dihexyl phthlate (DHP)                                                                           62.5                                                         Diisodecyl phthlate(DIDP)                                                                        62.5                                                         CaCO.sub.3        250                                                          ______________________________________                                          *Occidental 6482A medium molecular weight PVC homopolymer, inherent            viscosity 1.07 (ASTM D1243), K Value(Fikenstscher)71, specific gravity         1.414 (ASTM D792), gelatin temperature 163° F., 100% passes throug      a 325 mesh sieve, Occidental Chemical Corp., Pottstown, Pa.                    Borden VC265PVC copolymer plastisol blending resin containing 4% vinyl         acetate, 33-40 micron avg. particle size powder, Borden, Inc., Columbus,       Ohio.                                                                          CaCO.sub.3 --Atomite brand CaCO.sub.3, 3 micron mean particle size,            Thompson, Weineman and Company, Cartersville, Georgia.                   

Varying levels of adhesion promoter were utilized as follows:

                  TABLE 2                                                          ______________________________________                                         Formulation No.  Wt. Parts                                                     ______________________________________                                         204-65-1         10.17                                                         204-65-2         7.13                                                          204-65-3         4.75                                                          204-65-4         3.56                                                          204-65-5         2.38                                                          204-65-6         1.19                                                          204-65-7         0.59                                                          ______________________________________                                    

The adhesion promoter was Euretek 580 polyaminoamide adhesion promoter (amine value of 190, manufactured under U.S. Pat. No. 4,146,520, Sherex Chemical Company, Inc., Dublin, Ohio).

Brookfield viscosity measurements were taken on each formulation initially and thereafter at various intervals of time. The following data was recorded.

                                      TABLE 3                                      __________________________________________________________________________     Viscosity (cps)                                                                No.                                                                               RPM  Initial                                                                             3 days                                                                               7 days                                                                             17 days                                                                              24 days                                                                            32 days                                                                              45 days                                 __________________________________________________________________________     1  2.5  154,800                                                                             267,200                                                                              350,400                                                                            334,400                                                                              348,800                                                                            339,200                                                                              324,800                                    5    99,400                                                                              184,800                                                                              249,600                                                                            254,400                                                                              255,200                                                                            244,800                                                                              232,800                                    10   66,600                                                                              125,600                                                                              174,800                                                                            177,200                                                                              178,800                                                                            176,400                                                                              165,600                                    20   47,350                                                                               91,800                                                                              129,000                                                                            130,600                                                                              133,000                                                                            134,600                                                                              125,600                                    R     3.27                                                                                 2.91                                                                                 2.72                                                                               2.56                                                                                 2.62                                                                               2.52                                                                                 2.59                                     yield                                                                                2,770                                                                               4,120                                                                                5,040                                                                              4,000                                                                                4,680                                                                              4,720                                                                               4,500                                   2  2.5  143,200                                                                             283,200                                                                              302,400                                                                            304,000                                                                              272,000                                                                            267,200                                                                              275,200                                    5    91,600                                                                              188,800                                                                              199,200                                                                            209,600                                                                              175,200                                                                            177,600                                                                              185,600                                    10   59,300                                                                              122,800                                                                              130,000                                                                            138,800                                                                              117,600                                                                            119,600                                                                              124,800                                    20   40,800                                                                               85,600                                                                               90,800                                                                             97,400                                                                               84,800                                                                             87,200                                                                               90,800                                    R     3.58                                                                                 3.31                                                                                 3.33                                                                               3.12                                                                                 3.21                                                                               3.06                                                                                 3.03                                     yield                                                                                2,580                                                                               4,720                                                                                5,160                                                                              4,720                                                                                4,840                                                                              4,480                                                                                4,480                                  3  2.5  214,400                                                                             276,800                                                                              312,000                                                                            313,600                                                                              324,800                                                                            262,400                                                                              244,800                                    5    137,600                                                                             171,200                                                                              192,800                                                                            197,600                                                                              205,600                                                                            164,800                                                                              152,800                                    10   87,200                                                                              106,400                                                                              120,400                                                                            126,400                                                                              134,800                                                                            105,600                                                                                98,400                                   20   57,200                                                                               69,200                                                                               78,000                                                                             85,800                                                                               93,800                                                                             72,600                                                                               65,400                                    R     3.75                                                                                 4.00                                                                                 4.00                                                                               3.66                                                                                 3.46                                                                               4.47                                                                                 3.74                                     yield                                                                                3,840                                                                               5,280                                                                                5,960                                                                              5,800                                                                                5,960                                                                              4,880                                                                                4,600                                  4  2.5  228,800                                                                             320,000                                                                              342,400                                                                            328,000                                                                              307,200                                                                            270,400                                                                              276,800                                    5    147,200                                                                             200,800                                                                              212,800                                                                            203,200                                                                              189,600                                                                            168,800                                                                              173,600                                    10   93,600                                                                              124,800                                                                              133,200                                                                            127,600                                                                              118,400                                                                            105,600                                                                              109,600                                    20   61,200                                                                               80,600                                                                               88,400                                                                             83,600                                                                               78,400                                                                             70,200                                                                               73,600                                    R     3.74                                                                                 3.97                                                                                 3.87                                                                               3.92                                                                                 3.92                                                                               3.85                                                                                 1.59                                     yield                                                                                4,080                                                                               5,960                                                                                6,480                                                                              6,240                                                                                5,880                                                                              5,080                                                                                5,000                                  5  2.5  275,200                                                                             347,200                                                                              315,200                                                                            328,000                                                                              310,400                                                                            289,600                                                                              276,800                                    5    177,600                                                                             216,800                                                                              189,600                                                                            202,400                                                                              192,000                                                                            178,400                                                                              173,600                                    10   113,200                                                                             134,000                                                                              114,000                                                                            124,800                                                                              119,200                                                                            109,600                                                                              109,200                                    20   73,200                                                                               85,800                                                                               73,600                                                                             80,400                                                                               76,800                                                                             71,400                                                                               72,800                                    R     3.76                                                                                 4.05                                                                                 4.28                                                                               4.08                                                                                 4.04                                                                               4.06                                                                                 3.40                                     yield                                                                                4,880                                                                               6,520                                                                                6,280                                                                              6,280                                                                                5,920                                                                              5,560                                                                                5,160                                  6  2.5  345,600                                                                             398,400                                                                              361,600                                                                            342,400                                                                              360,000                                                                            342.400                                                                              318,400                                    5    245,600                                                                             246,400                                                                              224,000                                                                            208,800                                                                              218,400                                                                            209,600                                                                              197,600                                    10   158,400                                                                             150,800                                                                              136,400                                                                            127,200                                                                              131,600                                                                            126,800                                                                              120,800                                    20   99,800                                                                               93.600                                                                               84,800                                                                             78,800                                                                               82,200                                                                             78,800                                                                               75,600                                    R     3.46                                                                                 4.26                                                                                 4.26                                                                               4.35                                                                                 4.38                                                                               4.35                                                                                 4.21                                     yield                                                                                5,000                                                                               7,600                                                                                6,880                                                                              6,680                                                                                7,080                                                                              6,640                                                                                6,040                                  7  2.5  387,200                                                                             449,600                                                                              420,700                                                                            424,000                                                                              414,400                                                                            392,000                                                                              395,200                                    5    274,400                                                                             276,800                                                                              250,400                                                                            253,600                                                                              247,200                                                                            231,200                                                                              235,200                                    10   171,200                                                                             165,200                                                                              147,200                                                                            150,400                                                                              146,800                                                                            137,200                                                                              140,000                                    20   104,800                                                                              98,800                                                                               90,000                                                                             91,400                                                                               88,800                                                                             82,600                                                                               86,200                                    R     3.69                                                                                 4.55                                                                                 4.68                                                                               4.64                                                                                 4.67                                                                               4.75                                                                                 4.58                                     yield                                                                                5,640                                                                               8,640                                                                                8,520                                                                              85,20                                                                                8,360                                                                              8,040                                                                                8,00                                   __________________________________________________________________________      *Spindle #6 for 20465-1 and 2, and Spindle #7 for all other samples.           R is a measure of the degree of thixotropy and is calculated by dividing       the viscosity at 2.5 rpm by the viscosity at 20 rpm.                           Yield is a measure of the force required to move the plastisol (thickness      of the plastisol) and is calculated as follows:                                ##STR1##                                                                 

Advantageously, the viscosity should stabilize over time. The above-tabulated data demonstrates such viscosity stability.

Each formulation was drawn down (0.020 inch coating) or primed steel panels (Uni-Prime coated panels, PPG Industries, used in all examples) and baked for 20 minutes at 121° C. Each coating had good adhesion to the panels except for 204-65-7, indicating that the promoter level was too low.

The coated panels then were coated with a white enamel paint (an automotive topcoat based on melamine and a hydroxyl-acrylic resin with an acid catalyst, supplied by PPG Industries, Pittsburgh, Pa.) The topcoated panels were baked at 121° C. for 30 minutes. All samples were slightly tacky and eventually intercoat adhesion was lost (about 50 days). This demonstrates the difficulties encountered in curing an acid catalyzed topcoat over a primer higher in amine value. Thus, while metal adhesion and controlled age viscosity were good, paintability was lacking.

EXAMPLE 2

Plasticizer studies extended to various blends in order to retain control age viscosity but improve paintability. The basic formulation studies was as follows:

                  TABLE 4                                                          ______________________________________                                         Ingredient*     Amount (wt.-parts)                                             ______________________________________                                         Occidental 6482 60                                                             Borden VC265    40                                                             CaCO.sub.3      100                                                            Talc            20                                                             Silica           1                                                             Euretek 580 promoter                                                                           3.21 phr                                                       ______________________________________                                          Talc  Mistron ZCS grade talc, Cypress Industrial Minerals                      Silica  CabO-Sil brand fumed silica, Cabot Corporation.                        Promotor  phr is weight parts per hundred weight parts of PVC.           

The various plasticizer/promoter phases evaluated are set forth below:

                  TABLE 5                                                          ______________________________________                                                  Formulation No. 204-88 (wt.-parts)                                    Ingredient 1     2        3   4      5   6                                     ______________________________________                                         DIHP       50    50       50  50     50  50                                    DHP        10    20       25  50     50  100                                   Monoiso-   40    30       25  --     --  40                                    propyl                                                                         biphenyl                                                                       ______________________________________                                    

In formulations 1-3 and 5, the promoter was added to the plasticizer mix slightly warmed until homogeneous. In formulations 4 and 6, the promoter was added after the plastisol was made. Age viscosity measurements were taken as set forth below.

                  TABLE 6                                                          ______________________________________                                         Viscosity (cps)                                                                No.  RPM     Initial 1 day 4 days                                                                               11 days                                                                              22 days                                                                              34 days                           ______________________________________                                         1    2.5     217,600 188,800                                                                              273,600                                                                              236,800                                                                              251,200                                                                              244,800                                5       128,800 113,600                                                                              179,200                                                                              154,400                                                                              172,000                                                                              174,400                                10       79,600  69,600                                                                              111,600                                                                              101,200                                                                              119,600                                                                              118,800                                20       50,800  46,800                                                                               74,400                                                                               69,000                                                                               84,200                                                                               85,800                                R         4.28    4.03                                                                                 3.68                                                                                 3.43                                                                                 2.98                                                                                 2.85                                 yield    4,440   3,760                                                                                4,720                                                                                4,120                                                                                3,960                                                                                3,520                            2    2.5     224,000 212,800                                                                              212,400                                                                              300,800                                                                              304,000                                                                              308,800                                5       132,800 126,400                                                                              165,600                                                                              201,600                                                                              212,000                                                                              211,200                                10       80,800  77,600                                                                              105,200                                                                              141,600                                                                              150,400                                                                              148,800                                20       50,800  49,400                                                                               69,600                                                                              103,400                                                                              115,800                                                                              117,400                                R         4.41    4.31                                                                                 3.77                                                                                 2.91                                                                                 2.63                                                                                 2.63                                 yield    4,560   4,320                                                                                4,840                                                                                4,960                                                                                4,600                                                                                4,880                            3    2.5     220,800 192,000                                                                              241,600                                                                              246,400                                                                              275,200                                                                              275,200                                5       122,400 115,200                                                                              148,000                                                                              153,600                                                                              172,800                                                                              180,800                                10       73,200  70,400                                                                               93,600                                                                               97,200                                                                              113,200                                                                               25,200                                20       46,000  45,600                                                                               63,600                                                                               65,600                                                                               77,200                                                                                88,800                               R         4.80    4.21                                                                                 3.80                                                                                 3.76                                                                                 3.56                                                                                 3.10                                 yield    4,920   3,840                                                                                4,680                                                                                4,640                                                                                5,120                                                                                4,720                            4    2.5     217,600 214,400                                                                              227,200                                                                              235,200                                                                              233,600                                                                              246,400                                5       131,200 128,800                                                                              139,200                                                                              140,800                                                                              139,200                                                                              150,400                                10       81,600  79,600                                                                               85,600                                                                               86,000                                                                               86,800                                                                               95,200                                20       51,400  50,800                                                                               54,600                                                                               56,200                                                                               56,400                                                                               63,400                                R         4.23    4.22                                                                                 4.16                                                                                 4.19                                                                                 4.14                                                                                 3.89                                 yield    4,320   4,280                                                                                4,400                                                                                4.720                                                                                4,720                                                                                4,800                            5    2.5     230,400 204,800                                                                              214,400                                                                              212,800                                                                              217,600                                                                              217,600                                5       139,200 125,600                                                                              130,400                                                                              128,800                                                                              131,200                                                                              132,800                                10       85,600  78,400                                                                               81,600                                                                               79,200                                                                               81,600                                                                               82,400                                20       53,800  50,800                                                                               52,600                                                                               51,200                                                                               51,600                                                                               53,400                                R         4.28    4.03                                                                                `4.08                                                                                 4.16                                                                                 4.22                                                                                 4.07                                 yield    4,560   3,960                                                                                4,200                                                                                4,200                                                                                4,320                                                                                4,240                            6    2.5     193,600 204,800                                                                              225,600                                                                              196,800                                                                              249,600                                                                              254,400                                5       124,800 128,800                                                                              138,400                                                                              122,400                                                                              156,800                                                                              161,600                                10       75,200  78,400                                                                               85,600                                                                               74,800                                                                               08,000                                                                              109,600                                20       46,200  50,000                                                                               54,600                                                                               51,600                                                                               64,800                                                                               70,600                                R         4.19    4.09                                                                                 4.13                                                                                 3.81                                                                                 3.85                                                                                 3.32                                 yield    3,440   3,800                                                                                4,360                                                                                3,720                                                                                4,640                                                                                4,640                            ______________________________________                                          Spindle #7 for all samples.                                              

Coatings on primed steel panels (0.020 inch thickness) were baked at 121° C. for 20 minutes. All films adhered well except No. 204-88-5 (control). The acid catalyst topcoat of Example 1 was applied over the cured plastisols and baked at 121° C. for 30 minutes (wet-on-dry). Nos. 1-3 were dry while Nos. 4 and 5 were slightly tacky. Thus, the paintability of the plastisol had been improved by the addition of the secondary plasticizer solvent, monoisopropyl biphenyl. The amount of secondary plasticizer solvent appeared to be a bit low in Nos. 2 and 3, so that the formulation of this example appears to require at least about 40 weight parts of monoisopropyl biphenyl in order for paintability to be realized.

EXAMPLE 3

The basic formulation of Example 2 (Table 4) was studied again at higher levels of monoisopropyl biphenyl: 50 wt.-parts for 204-96-1 and 70 wt.-parts for 204-96-2. Again, the technique of blending the adhesion promoter into the plasticizer blend prior to making the plastisol was utilized. The age viscosity data recorded is set forth below.

                                      TABLE 7                                      __________________________________________________________________________     Viscosity (cps)                                                                No.                                                                               RPM Initial                                                                             1 day                                                                               6 days                                                                              14 days                                                                             21 days                                                                             30 days                                                                             45 days                                   __________________________________________________________________________        3.72  1                                                                     2.5    142,000                                                                             161,600                                                                             172,000                                                                             174,400                                                                             815,6000                                                                            195,200                                                                             180,000                                          5    86,600                                                                              99,200                                                                              106,400                                                                             115,200                                                                             120,800                                                                             126,400  111,400                                 10   55,100                                                                              62,900                                                                              67,800                                                                              74,400                                                                              78,800                                                                              84,000 71,700                                    20   36,350                                                                              41,650                                                                              46,200                                                                              48,200                                                                              52,800                                                                              56,600 47,100                                    R     3.91                                                                                3.88                                                                                3.725                                                                              3.62  3.52                                                                                3.45   3.77                                     yield                                                                                2,770                                                                               3,120                                                                               3,280                                                                               2,960                                                                               3,240                                                                               3,440  3,430                             2      2.5  174,400                                                                             118,400                                                                             105,600                                                                             124,800                                                                             134,400                                                                             140,800  163,200                                 5    115,600                                                                             105,600                                                                             98,400                                                                              101,600                                                                             104,400                                                                             123,200  122,400                                 10   74,700                                                                              88,400                                                                              90,400                                                                              96,400                                                                              98,800                                                                              99,200 101,600                                   20   48,300                                                                              64,800                                                                              69,200                                                                              79,200                                                                              81,600                                                                              77,400  82,400                                   R     3.61                                                                                1.83                                                                                1.33                                                                                1.58                                                                                1.65                                                                                1.82   1.98                                     yield                                                                                2,940                                                                                640                                                                                 360                                                                                1,160                                                                               1,000                                                                                880  2,040                              __________________________________________________________________________      Spindle #6 for Initial, 1 day, and 6 days for No. 1 and for Initial for        No. 2;                                                                         Spindle #7 for all other samples.                                        

Each plastisol exhibited good adhesion to the steel panels (bake protocol of 121° C. for 20 minutes). The acid catalyzed topcoat of Example 1 was applied wet-on-dry and wet-on-wet baking at 121° C. for 30 minutes for both. The topcoat was not tacky for both systems. Note the slightly increased secondary solvent levels used compared to Example 2. Thus, the ability to achieve paintability while retaining adhesion to metal has been achieved.

EXAMPLE 4

The following formulations were studied.

                  TABLE 8                                                          ______________________________________                                         Formulation No. 204-147                                                                           (wt-parts)                                                  Ingredient           1      2                                                  ______________________________________                                         Occidental 6482      60     60                                                 Borden VC265         40     40                                                 CaCO.sub.3           200    200                                                Talc                 10     10                                                 DIDP                 60     60                                                 Monoisopropyl biphenyl                                                                              40     40                                                 Euretek 580 promoter  3      3                                                 ______________________________________                                    

The plasticizer/promoter blend of No. 1 was mixed at room temperature and then added to the plastisol. The plasticizer/promoter blend of No. 2 was mixed at 72° C. and then added to the plastisol. The effects of temperature during the formulating, thus, were being studied.

Both plastisols were coated on steel panels and subjected to wet-on-dry and wet-on-wet topcoating as in Example 3. No apparent performance difference between the two formulations observed.

EXAMPLE 5

Various secondary plasticizer solvents were studied utilizing the basic formulation of Example 2. The various plasticizer blends studied are set forth below:

                  TABLE 9                                                          ______________________________________                                         Formulation No. 204-98                                                                       (wt.-parts)                                                      Ingredient      1          2     3                                             ______________________________________                                         DIDP            50         50    50                                            DHP             10         10    10                                            Butylated biphenyl                                                                             40         --    --                                            Diisopropyl biphenyl                                                                           --         40    --                                            Phenylxyleyl ethane                                                                            --         --    40                                            ______________________________________                                    

The plasticizer/promoter blends were made and then added to the remaining ingredients, as described above. Age viscosity data are set forth below.

                  TABLE 9                                                          ______________________________________                                         Viscosity (cps)                                                                No.   RPM     Initial  6 days                                                                               14 days                                                                               30 days                                                                              45 days                              ______________________________________                                         1     2.5     212,800  198,400                                                                              190,400                                                                               201,600                                                                              185,600                                    5       147,200  120,800                                                                              113,600                                                                               121,600                                                                              111,200                                    10       96,000   74,800                                                                               70,400                                                                                75,600                                                                               69,600                                    20       62,400   48,200                                                                               45,400                                                                                50,600                                                                               45,000                                    R         3.41     4.12                                                                                 4.19   3.98                                                                                 4.12                                     yield    3,280    3,880                                                                                3,840  4,000                                                                                3,720                               2     2.5     259,200  225,600                                                                              206,400                                                                               214,400                                                                              206,400                                    5       172,000  136,800                                                                              124,800                                                                               131,200                                                                              123,200                                    10      106,800   84,800                                                                               76,400                                                                                82,000                                                                               77,200                                    20       68,200   54,400                                                                               50,600                                                                                55,400                                                                               50,800                                    R         3.80     4.15                                                                                 4.08   3.87                                                                                 4.06                                     yield    4,360    4,440                                                                                4,080  4,160                                                                                4,160                               3     2.5     171,200  195,200                                                                              195,200                                                                               188,800                                                                              190,400                                    5       143,200  125,600                                                                              120,800                                                                               117,600                                                                              121,600                                    10       98,800   78,000                                                                               75,600                                                                                71,200                                                                               74,800                                    20       64,000   51,600                                                                               50,800                                                                                47,200                                                                               49,600                                    R         2.68     3.78                                                                                 3.84   4.00                                                                                 3.84                                     yield    1,400    3.480                                                                                3,720  3,560                                                                                3,440                               ______________________________________                                          Spindle #7 for all samples.                                              

The formulations were coated and cured on steel panels (121° C. for 20 minutes) and topcoated wet-on-dry and wet-on-wet as in the previous examples. Again, good adhesion to the substrates was achieved. The wet-on-dry topcoats also were tack free while the wet-on-wet topcoats were very slightly tacky. Thus, the efficacy of additional aromatic secondary plasticizer solvents is demonstrated.

EXAMPLE 6

The following formulations were made as described above.

                  TABLE 10                                                         ______________________________________                                         Formulation no. 204-116                                                                       (wt.-parts)                                                     Ingredient       1      2        3    4                                        ______________________________________                                         Occidental 6482  60     60       60   60                                       Borden VC265     40     40       40   40                                       CaCO.sub.3       200    200      200  200                                      DIDP             60     60       60   30                                       DHP              --     --       --   30                                       Euretek 580 promoter                                                                            5      3        3    3                                        Monoisopropyl biphenyl                                                                          40     40       --   --                                       Diethylene glycol                                                                               --     --       40   40                                       monoethyl ether                                                                ______________________________________                                    

Control age viscosity data recorded is set forth below.

                  TABLE 11                                                         ______________________________________                                         Viscosity (cps)                                                                No.  RPM     Initial  3 days 14 days                                                                               25 days                                                                              31 days                              ______________________________________                                         1    2.5     211,200  206,400                                                                               233,600                                                                               241,600                                                                              284,800                                   5       171,200  196,800                                                                               220,800                                                                               215,200                                                                              237,600                                   10      115,200  153,200                                                                               175,600                                                                               164,400                                                                              180,800                                   20      79,600   106,600                                                                               126,400                                                                               121,600                                                                              137,600                                   R        2.65     1.94   1.85    1.99                                                                                2.07                                     yield   2,000      480    640   1,320                                                                                2,360                               2    2.5     219,200  256,000                                                                               262,400                                                                               278,400                                                                              281,600                                   5       144,000  211,200                                                                               228,800                                                                               246,400                                                                              231,200                                   10      98,400   153,600                                                                               169,200                                                                               180,000                                                                              172,400                                   20      60,600   109,400                                                                               115,400                                                                               132,400                                                                              124,200                                   R        3.62     2.34   2.27    2.10                                                                                2.27                                     yield   3,760     2,240  1,680  1,600                                                                                2,520                               3    2.5     6,240    15,520 33,200  33,200                                                                              34,400                                    5       5,040    12,080 23,200  25,000                                                                              25,600                                    10      4,320     9,760 17,800  20,400                                                                              20,500                                    20      3,860      8,120                                                                               14,600  16,550                                                                              16,750                                    R        1.62     1.91   2.27    2.00                                                                                2.05                                     yield     60       172    500     410                                                                                 440                                4    2.5     5,440    15,360 32,800  40,400                                                                              44,800                                    5       4,480    12,240 25,000  31,400                                                                              34,800                                    10      3,840    10,160 20,200  25,600                                                                              28,100                                    30      3,340     8,920 17,050  21,950                                                                              23,850                                    R        1.63     1.72   1.92    1.84                                                                                1.88                                     yield     48       156    390     450                                                                                 500                                ______________________________________                                          Spindle #7 for No. 1 and No. 2; Spindle #5 for Initial and 3 days for No.      3 and No. 4;                                                                   Spindle #6 for remaining samples.                                        

The plastisols were coated on panels (121° C. for 20 minutes) and topcoated wet-on-dry as described in the previous examples. Again, good substrate adhesion was achieved. The topcoats were dry for Nos. 2, 3, and 4, and only very slightly tacky for No. 1. Again, the low temperature paintability of the inventive plastisols is demonstrated.

EXAMPLE 7

Additional studies of the ether secondary plasticizer solvent were undertaken on the following formulations.

                  TABLE 12                                                         ______________________________________                                         Formulation No. 204-98                                                                      (wt.-parts)                                                       Ingredient     1           2      3                                            ______________________________________                                         Occidental 6482                                                                               60          60     60                                           Borden VC265   40          40     40                                           CaCO.sub.3     200         200    200                                          DIDP           90          80     105                                          Diethyleneglycol                                                                              10          20     20                                           monoethyl ether                                                                Euretek 580 promoter                                                                           3           3      3                                           ______________________________________                                    

Control age viscosity data is set forth below.

                  TABLE 13                                                         ______________________________________                                         Viscosity (cps)                                                                No.  RPM     Initial 1 day 3 days                                                                               10 days                                                                              21 days                                                                              24 days                           ______________________________________                                         1    2.5     128,800 170,400                                                                              249,600                                                                              283,200                                                                              267,200                                                                              254,400                                5       78,600  104,000                                                                              151,200                                                                              177,600                                                                              167,200                                                                              158,400                                10      50,200  66,400                                                                               96,400                                                                               114,400                                                                              108,400                                                                              102,400                                20      33,950  44,900                                                                               63,200                                                                               79,200                                                                               74,800                                                                               70,800                                 R       3.79    3.80  3.95  3.58  3.57  3.59                                   yield   2,510   3,320 4,920 5,280 5,000 4,800                             2    2.5     65,600  98,400                                                                               135,200                                                                              161,200                                                                              170,800                                                                              164,800                                5       40,200  59,400                                                                               82,400                                                                               96,800                                                                               106,600                                                                              100,200                                10      25,600  38,200                                                                               52,600                                                                               63,800                                                                               69,700                                                                               64,900                                 20      17,700  25,800                                                                               36,000                                                                               45,050                                                                               47,350                                                                               44,950                                 R       3.71    3.82  3.76  3.58  3.61  3.67                                   yield   1,270   1,950 2,640 3,220 3,210 3,230                             3    2.5     35,680  59,520                                                                               82,720                                                                               109,600                                                                              105,600                                                                              101,200                                5       20,880  35,360                                                                               48,960                                                                               65,200                                                                               63,600                                                                               60,400                                 10      18,000  22,080                                                                               30,240                                                                               40,300                                                                               39,600                                                                               37,300                                 20      8,620   14,500                                                                               19,600                                                                               26,300                                                                               26,200                                                                               24,600                                 R       4.14    4.10  4.22  4.17  4.03  4.11                                   yield   740     1,208 1,688 2,220 2,100 2,040                             ______________________________________                                          Spindle #6 for No. 1 and No. 2; Spindle #5 for No. 3.                    

Good adhesion to steel panels again was achieved. The wet-on-dry topcoats (121° C. for 30 minutes) also were dry. The efficacy of the ether secondary plasticizer solvent again is demonstrated.

EXAMPLE 8

Formulation No. 204-118-1 (Example 7) was evaluated again along with an equivalent formulation which used a different adhesion promoter (No. 2) at the same level: Euretek 555 polyaminoamide-polyimidazole adhesion promoter (amine value of 380; Gardner color of 12: 8.1 lb/gal. at 82.2° C.; Viscosity profile (Brookfield LVT, spindle 34) of 17,000 cps at 43.3° C., 13,000 cps at 48.9° C., 9,000 cps at 54.5° C., 4,000 cps at 60.0° C., and 2,800 cps at 65.6° C.; Sherex Chemical Company, Inc., Dublin, Ohio). The control age viscosity data recorded is set forth below.

                  TABLE 14                                                         ______________________________________                                         Viscosity (cps)                                                                No.  RPM     Initial 1 day 3 days                                                                               10 days                                                                              21 days                                                                              24 days                           ______________________________________                                         1    2.5     128,800 170,400                                                                              249,600                                                                              283,200                                                                              267,200                                                                              254,400                                5       78,600  104,000                                                                              151,200                                                                              177,600                                                                              167,200                                                                              158,400                                10      50,200  66,400                                                                               96,400                                                                               114,400                                                                              108,400                                                                              102,400                                20      33,950  44,900                                                                               63,200                                                                               79,200                                                                               74,800                                                                               70,800                                 R       3.79    3.80  3.95  3.58  3.57  3.59                                   yield   2,510   3,320 4,920 5,280 5,000 4,800                             2    2.5     130,800 145,600                                                                              185,600                                                                              154,800                                                                              154,800                                      5       82,000  87,800                                                                               93,600                                                                               94,600                                                                               95,800                                       10      52,700  55,700                                                                               59,800                                                                               61,400                                                                               62,600                                       20      35,650  37,900                                                                               41,950                                                                               42,600                                                                               43,800                                  ______________________________________                                          See Example 7 for No. 1; Spindle #6 for No. 2.                           

Panel coatings and wet-on-dry acid catalyzed topcoats were applied as in the previous examples. Good panel adhesion was achieved. The topcoat on Formulation No. 204-118-1 was dry while the topcoat of Formulation No. 204-126-2 was only slightly tacky.

EXAMPLE 9

The following formulations were made:

                  TABLE 15                                                         ______________________________________                                         Formulation No. 204-120                                                                     (wt.-parts)                                                       Ingredient     1           2      3                                            ______________________________________                                         Occidental 6482                                                                               60          60     60                                           Borden VC265   40          40     40                                           CaCO.sub.3     200         200    200                                          DIDP           90          80     55                                           Diethylene glycol                                                                             10          20     20                                           monoethyl ether                                                                Euretek 580 promoter                                                                           3           3      3                                           ______________________________________                                    

Control age viscosity data is set forth below.

                  TABLE 16                                                         ______________________________________                                         Viscosity (cps)                                                                No.     RPM    Initial   1 day  10 days                                                                               21 days                                 ______________________________________                                         1       2.5    108,800   158,400                                                                               334,400                                                                               318,400                                         5      66,600    96,800 212,800                                                                               203,200                                         10     43,300    61,600 137,600                                                                               131,200                                         20     30,000    41,600 92,800 90,800                                          R      3.63      3.81   3.60   3.51                                            yield  2,110     3,080  6,080  5,760                                   2       2.5    20,400    44,000 225,600                                                                               249,600                                         5      13,400    27,600 136,800                                                                               150,400                                         10     10,200    18,900 86,800 10,800                                          20     7,850     13,800 56,600 71,200                                          R      2.60      3.19   3.99   3.51                                            yield  350       820    4,440  4,960                                   3       2.5    22,800    40,000 313,600                                                                               304,000                                         5      19,000    32,200 217,600                                                                               202,400                                         10     16,300    26,100 110,400                                                                               137,600                                         20     14,700    22,950 81,400 102,800                                         R      1.55      1.83   3.85   2.96                                            yield  190       490    4,800  5,080                                   ______________________________________                                          Spindle #6 for Initial and 1 day; Spindle #7 for all other samples.      

Panel and topcoat testing revealed that good panel adhesion still was present but that the wet-on-dry topcoats (121° C. for 30 minutes) were slightly tacky. The reason for the dimunition in performance of this butyl ether solvent compared to the ethyl ether version is not understood presently.

EXAMPLE 10

The following formulations were made.

    ______________________________________                                         Formulation No. 204                                                                         (wt.-parts)                                                       Ingredient*    103-1  103-2  105-1                                                                               105-2                                                                               138-1                                                                               138-2                              ______________________________________                                         Occidental 6482                                                                               60     60     60   60   60   60                                 Borden VC265   40     40     40   40   40   40                                 CaCO.sub.3     100    100    100  100  200  200                                Talc           20     20     20   20   --   --                                 Silica          1      1      1    1   --   --                                 DIDP           30     20     50   30   90   80                                 DHP            30     20     25   30   --   --                                 Monoisopropyl biphenyl                                                                        20     30     --   --   --   --                                 Propylene glycol                                                                              20     30     --   --   --   --                                 dibenzoate                                                                     Ethyl toluene sulfon amide                                                                    --     --     25   40   --   --                                 (ortho and para isomer                                                         mixture)                                                                       Ethoxylated nonyl phenol                                                                      --     --     --   --   10   20                                 ______________________________________                                          *Euretek 580 promoter added at 1% by weight in all formulations.               Ethoxylated nonyl phenolIgepal CO630 nonylphenoxy poly(ethyleneoxy)            ethanol, GAF Corporation.                                                

While the aromatic ester, the sulfonamide, and the nonyl phenol solvents all solvated the adhesion promoter, wet-on-dry paintability was lacking. Ester solvents appear not to be beneficial due to postulated undesirable interaction with other ingredients. The sulfonamide solvent adds more amine value to the plastisol whidh is not desirable for achieving cure of the acid catalyzed topcoat. The ethoxylated nonyl phenol solvent should have functioned properly according to current understanding of the invention. Perhaps different levels or degrees of ethoxylation will enable this solvent to function is plastisol. 

I claim:
 1. A method for coating a metal substrate which comprises:(a) applying a plastisol composition comprising a finely-divided vinyl chloride polymer, filler, a primary plasticizer, and a polyaminoamide-polyimidazoline adhesion promoter, said plastisol including a plasticizer/promoter phase comprising said primary plasticizer, said adhesion promoter, and an effective amount of a secondary plasticizer nonionic solvent effective in solvating said adhesion promoter in said plasticizer/promoter phase, said plasticizer/promoter phase being preformed and added to the remaining ingredients of said plastisol composition; (b) applying an acid-catalyzed topcoat over said plastisol composition; and (c) heating said coated metal substrate to cure said plastisol composition and said topcoat.
 2. The method of claim 1 wherein said plastisol composition on said metal substrate is heated for its curing prior to applying said topcoat thereto.
 3. The method of claim 1 wherein said secondary plasticizer nonionic solvent is selected from the group consisting of monoisopropyl biphenyl, diethylene glycol monoethyl ether, diisopropyl biphenyl, phenylxyleyl ethane, butylated biphenyl, and mixtures thereof.
 4. The method of claim 2 wherein said secondary plasticizer nonionic solvent is selected from the group consisting of monoisopropyl biphenyl, diethylene glycol monoethyl ether, diisopropyl biphenyl, phenylxyleyl ethane, butylated biphenyl, and mixtures thereof.
 5. The method of claim 1 wherein the proportion of secondary plasticizer ranges from between about 10 to 70 weight parts, said primary plasticizer ranges from between about 20 ad 200 weight parts, and said promoter ranges from between about 1 and 10 weight parts, all weight parts based on 100 weight parts of said vinyl chloride polymer.
 6. The method of claim 2 wherein the proportion of secondary plasticizer ranges from between about 10 to 70 weight parts, said primary plasticizer ranges from between about 20 ad 200 weight parts, and said promoter ranges from between about 1 and 10 weight parts, all weight parts based on 100 weight parts of said vinyl chloride polymer. 